Related Articles

Cement board, also known as backerboard, is used as an underlayment for tile flooring and walls. The boards typically come in 3-foot by 5-foot sheets and can be cut to size. Backerboard, once installed, does not move or expand. This helps prevent tiles from shifting and grout from cracking. There are several manufacturers of backerboard, but most are installed in a similar fashion. On flooring applications, the backerboard is installed with thinset mortar and screws over the wood subfloor.

1

Measure the length and width of the floor to be tiles to determine how many sheets of backerboard are required. Since most backerboard sheets are 3-foot by 5-foot, each sheet covers 15 square feet. Some manufacturers also sell 4-foot by 8-foot sheets, but they are harder to find.

2

Plan the layout of the backerboard sheets prior to installing them. Stagger the joints by one-half of a sheet wherever possible. Lay the sheets down on the subfloor as a test run.

3

Mark the sheets that need to be cut. Score the sheets that need cutting with a carbide backerboard cutter. Snap the sheet along the cut line. Remove the backerboards from the floor and sweep and vacuum the floor.

4

Mix a bucket of thinset mortar in mixing bucket according to the manufacturer's instructions. Apply the mortar directly to the wood sublfoor with a 1/4-inch U-notched trowel.

5

Lay the backerboard down one sheet a time. Screw the backerboard to the sublfloor with 1 1/4-inch backerboard screws. Screw the backerboard approximately every 8 inches or at the locations marked on the sheet by the manufacturer. Stay at least 3/8 inch away from edges and corners to prevent splitting.

6

Apply thinset mortar to all seams and joints. Place mesh backerboard tape into the mortar, then smooth it into the mortar with the flat side of the notched trowel.

Things You Will Need

Backerboard

Measuring tape

Pencil

Carbide backerboard cutter

Vacuum cleaner

Thinset mortar

1/4-inch U-notched trowel

Mixing bucket

Backerboard screws

Drill/driver

Mesh backerboard tape

Tip

While 1/4-inch-thick cement board is typically used for flooring, use 1/2-inch-thick board instead if you can, as it makes the floor even stronger. However, this may not be possible, as it may raise the overall height of the finished floor, creating threshold transition problems.

Warning

Always use backerboard screws. While some types of roofing nails are approved by the manufacturers, screws are much stronger and do not work loose over time.

About the Author

Emrah Oruc is a general contractor, freelance writer and former race-car mechanic who has written professionally since 2000. He has been published in "The Family Handyman" magazine and has experience as a consultant developing and delivering end-user training. Oruc holds a Bachelor of Arts in political science and a minor in economics from the University of Delaware.